DESCRIPTION: Chert is the name given to
some microcrystalline quartz -- see following discussion under Colors. Colors - typically white, diverse gray hues,
black, brown or yellowish, and rarely red, pink, yellow, green
or blue; uncommonly banded. Color sometimes leads to problems so
far as designating a given material chert rather than jasper;
indeed, some people consider jasper to be a colored variety of
chert. A "rule of thumb" -- albeit based on a subjective
criterion -- that I subscribe to is "if the
specimen exhibits so-to-speak attractive colors call it jasper,
otherwise call it chert." In addition, distinguishing some cherts
and jaspers from some chalcedony also requires subjective decisions.H. 7S.G. 2.55-2.65Light transmission - subtranslucent to
opaque
Luster - dull to porcelaneous, pearly or
even subvitreousBreakage - splintery to
conchoidal fracture Miscellany - most chert, especially that
widely called flint, is triboluminescent.

OTHER NAMES: To many geologists, the term
chert includes rocks frequently called flint and hornstone as well as
some
jasper. Some chert comprises units with extents that have
led to their being given formal stratigraphic unit designations (see
Appendix B, Glossary). Two examples are the Fort Payne Chert of the
southern
Appalachians and the Huntersville Chert of West Virginia, Tennessee,
Kentucky,
and Virginia. For the several terms that have been applied to
chert, see Hart (1927) as well
as those that follow:

"Caviar agate" - a misnomer sometimes applied to oolitic chert in the
marketplace.

Depalite - name given to an olive-green to
khaki-tan colored chert from Estill County, Kentucky.

<>Flint - white, gray, nearly black, or brown
chert widely used in former times for tools and weapons (e.g.,
arrow heads). Flint projectiles,
knives and scraping tools, dating to stone age cultures have been found
at widespread sites in, for example, the Near East and are said to have
been made and used "as early as 250,000 years ago at sites in the
el-Kowm basin, northeast of Palmyra, Syria" (Bergman, Azoury and
Seeden, 2012). Flint has also been called firestone,
apparently
because when struck it gives off sparks, which have been used for such
things as igniting tinder to trigger flintlock rifles. Indeed, the
ancient Greeks called flint pyrites lithos, and today's German
word for
flint is feurerstein (both words that translate to
firestone in English).

Hornstone -
term sometimes given, especially
in the past, to some cherts. This application is unfortunate
because hornstone has also been applied rather widely to other, quite
different rocks such as hornfels.

Ice stone - Ojibway name for white flint.

Mozarkite - a multicolored chert that occurs
sporadically in Missouri and in the Ozark Mountains of Arkansas.

Novaculite - a massive white chertlike
rock that very likely represents low-grade metamorphism of a precursor
chert; a good example occurs in the Devonian-Mississippian
stratigraphic sequence in the vicinity
of Hot Springs, Arkansas. Other names given to this rock include Arkansas
stone, galantine, Ouachita stone, razor stone, and Wayside stone.
Some novaculite is characterized by light pink, bluish or violet hues,
and that which is has been brecciated comprises rather attractive rough
material for fashioning diverse decorative pieces.

Oolitic (or pisolitic) chert - these rocks
from several localities have been tumbled, cut and polished as
cabochons for jewelry; fashioned into diverse ornaments; and
carved into such things as fetishes.

Utica jewelstone - name applied to a white
chert with gray and brown banding from LaSalle County, Illinois.

Zonite - name used locally -- e.g., in
Arizona -- for chert and diversely colored jasper.

USES: Cabochons for pendants and
bracelets;
tumbled for use in necklaces, bracelets, etc.; slabbed and
polished
for such things as paperweights. In addition, flint arrowheads
may be
considered
gemrocks because they are used widely as pendants, bolo slides, etc.
Although novaculite's primary use is as a hone or whetstone, it also
has
been fashioned, albeit infrequently, into diverse ornaments.

OCCURRENCES: Common as layers or nodules
in
limestone, including chalk, and dolostone formations.

NOTEWORTHY LOCALITIES: Widespread in
sedimentary rock terrains, especially those that include limestone
and/or dolostone formations. Three United States of America examples
have been recorded
as especially noteworthy: Flint Ridge, which extends eastward
from
near Newark, Licking Creek County almost to Zanesville, Muskingum
County,
Ohio (Anonymous, 1974)
[Also, a DVD, which I have NOT seen, about this locality was released
in 2008 -- it is said to have illustrations showing hundreds of
artifacts. Be forewarned that it has received mixed review.
I suspect its availability can be found on the internet.]
the area north of Utica, LaSalle County,
Illinois
(Mori, 1980); [and] near Yellville, Marion County,
Arkansas
(where a banded chert that takes an especially fine polish (etc.)
occurs -- see Trout (1983). In addition, some fine
"arrowhead
replicas" have recently been fashioned from a reddish brown and
off-white streaked chert from near Glendo, Wyoming.

REMARKS: Derivation of the term chert so
far as its application to this cryptocrystalline variety of quartz is
shrouded in, I suspect, the mists of 17th century England. In any
case, it [i.e.,chirts] was applied to chert masses in chalk in Staffordshire in
the literature by the 1680s (O.E.D.) Use of the term flint, long
applied to "hard stone" in general, had even more ancient roots -- at
least so far as its use in the literature; the diverse materials
to which it was been applied are too numerous to review here; for
a brief review, see the Oxford English Dictionary.

Although flint is chert is flint
is chert . . . etc., some people make the hardly useful
or
valid distinction that flint occurs as nodules whereas chert
constitutes layers or beds. But, as any geologist who has worked
with
these rocks
knows, even though some chert/flint may be described as having one
rather
than the other of these occurrences, others cannot. In fact,
chert/flint-bearing calcareous rocks commonly grade from zones
containing sporadic flint/chert nodules to zones with interbeds of
chert/flint.

Flint weapons and tools were made during the
"Stone age" in several places in Great Britain and continental Europe
(Shepherd, 1972). An artifact in the Oriental Institute
collections of the
University of Chicago bears the following label/caption: "IRAN:
Persepolis -
Tripod Bowl of Green Polished Chert, Achaemenid. From the
Treasury" is shown
on
the internet (www-oi.uchicago.edu); to date, however, I have been unable to gain further information about this
piece. Flint tools made by Native
Americans
from chert from Flint Ridge, Ohio have been found as far away as "on
the
Atlantic seaboard, in Louisiana, and as far west at Kansas . . .
and [this chert is also said to have been] of vital importance to early
Ohio settlers, who used it for starting fires and in flintlock guns,
which
were in use for two hundred years. [Furthermore,] a porous form of the
rock
was used for buhrstones to grind grain in early mills." (Anonymous,
1974).

Flint, as represented by the rather colorful
material from Flint Ridge, Licking County, is the official gemstone of
Ohio, and Mozarkite, whichis a varicolored (red, purple,
green
and reddish brown) chert that is fairly common in the Ozarks,
especially in Benton County, is the official state rock of
Missouri.